1. Field of the Invention
The present invention relates generally to improvements in the field of fiber optics, and particularly to advantageous aspects of systems and methods for reducing splice loss in optical fibers.
2. Description of Prior Art
An optical fiber transmission line typically includes more than one type of fiber. For example, in order to achieve a desired overall dispersion characteristic, an inverse dispersion fiber (IDF), which has a steeply negative dispersion slope, may be spliced to another type of fiber having a positive dispersion slope. However, IDF typically has a relatively narrow modefield diameter, whereas other types of fiber, such as a super large area (SLA) fiber, have a modefield diameter that is significantly larger than the IDF modefield diameter. This mismatch in modefield diameter may result in an unacceptably large amount of splice loss if the two fibers are spliced directly to each other.
One technique that has been developed to reduce splice loss between first and second fibers having different modefield diameters is the use of a bridge fiber having an intermediate modefield diameter. Instead of splicing the first fiber directly to the second fiber, the first fiber is spliced to a first end of the bridge fiber, and the second fiber is spliced to a second end of the bridge fiber. Depending upon the respective properties of the first fiber, second fiber, and bridge fiber, it is possible for the total splice loss using a bridge fiber to be significantly less than the splice loss that results when the first fiber is spliced directly to the second fiber. A bridge fiber technique is described, for example, in Edvold, B. and Gruner-Nielsen, L., xe2x80x9cNew Technique for Reducing the Splice Loss to Dispersion Compensating Fiber,xe2x80x9d European Conference on Optical Communication, 1996.
However, certain issues have arisen in connection with currently used bridge fibers and bridge fiber techniques. For example, under current practice, a typical length for a bridge fiber is 2 meters, or greater. Because a typical optical cable may include dozens of individual fibers, each to be spliced to a separate bridge fiber, the use of a 2-meter bridge fiber causes problems in packing the bridge fibers into a standard splice case, particularly in the field. In addition, although currently used bridge fibers and bridge fiber techniques can significantly reduce splice loss, there is an ongoing search for ways to reduce splice loss even further.
Aspects of the invention provide techniques for reducing splice loss by using an ultra-short bridge fiber to splice together a first fiber and a second fiber having different modefield diameters. The ultra-short bridge fiber has an intermediate modefield diameter between the modefield diameters of the first and second fibers. In a method according to an aspect of the invention, a first end of the ultra-short bridge fiber is spliced to a lead end of the first fiber at a first splice point. The bridge fiber is then cleaved at a predetermined distance away from the first splice point. A lead end of the second fiber is then spliced to the cleaved end of the bridge fiber at a second splice point. A single protective splint is then installed that covers the bridge fiber and the first and second splice points.
Additional features and advantages of the present invention will become apparent by reference to the following detailed description and accompanying drawings.